I posted in another thread a few days back, but here's how to switch to miles...

Press the display button repeatedly until you bring up the main (not the trip) odometer. Press and HOLD the button for a couple seconds- you should see the speedometer change to miles (it must have been reading in km/h if your RR is in km). Release the button and cycle through to RR and it should now be in miles.

Reread the post above yours - He says to select the main odometer reading (not the trip meters) and press and hold. It will change *everything* (speedometer, odometer and both trip odometers) from Kms to miles and back again. They all read in the same measurement together,either miles or Kms